Optical assembly having a housing for mounting optical lenses

ABSTRACT

A housing assembly for mounting a first lens and a second lens includes a first lens holder. The first lens holder includes a ring-shaped structure configured to mount the first lens. The housing assembly also includes a second lens holder including a cup-shaped structure. The cup-shaped structure includes an upper portion configured to mount the first lens holder, and a lower portion configured to mount the second lens.

BACKGROUND

An optical lens assembly used in various optical devices may include twoor more lens assembled and aligned with one another (e.g., aligned tohave a predetermined optical relationship) to form a monolithic lensassembly. For example, a head-mounted display (“HMD”) used inapplications such as virtual reality (“VR”) and/or augmented reality(“AR”) may include a monolithic pancake lens assembly (or pancake lens)for directing lights into a user's eyes. A pancake lens assembly may beformed by a plurality of optical elements, such as a lens, a waveplate,a reflector, a polarizer. In some implementations, a pancake lensassembly may be formed by gluing two lens cells together to form anintegral piece. The two lens cells, each including one or more opticalelements, may be aligned with respect to one another to achieve apredetermined optical property.

Some optical lens assemblies, such as certain pancake lens assemblies,may be polarization sensitive. That is, a polarization effect of a lensassembly may be sensitive to a mis-alignment between the opticalelements included in the lens assembly. Precise alignment between twolens cells may be required in order to achieve a predeterminedpolarization effect. In conventional systems, expensive equipment isused to achieve the required alignment precision when the opticalelements are assembled, which results in a high manufacturing cost. Inaddition, the output quality control cost is high due to the highfailure rate of the produced pancake lens assemblies (e.g., a highpercentage of the produced pancake lens assemblies are wasted due to thefailure to meet predetermined design specification). Finally, the cycletime for producing a pancake lens assembly is long in conventionalsystems.

The disclosed systems and methods can reduce the manufacturing costs,output quality control costs, and the cycle time.

BRIEF SUMMARY OF THE DISCLOSURE

One aspect of the present disclosure provides a housing assembly formounting a first lens and a second lens. The housing assembly includes afirst lens holder including a ring-shaped structure configured to mountthe first lens. The housing assembly also includes a second lens holderincluding a cup-shaped structure. The cup-shaped structure includes anupper portion configured to mount the first lens holder, and a lowerportion configured to mount the second lens.

Another aspect of the present disclosure provides an optical assembly.The optical assembly includes a first lens holder and a first lensmounted to the first lens holder. The optical assembly also includes asecond lens holder and a second lens mounted to the second lens holder.The first lens holder is mounted to the second lens holder, and thefirst lens is aligned with the second lens with a surface of the firstlens being in parallel with a surface of the second lens. The first lensholder is mounted to the second lens holder, and the first lens isaligned with the second lens with a surface of the first lens being inparallel with a surface of the second lens. The second lens holderincludes an upper portion configured to mount the first lens holder, anda lower portion configured to mount the second lens.

A further aspect of the present disclosure provides an optical device.The optical device includes an optical assembly. The optical assemblyincludes a first lens holder and a first lens mounted to the first lensholder. The optical assembly also includes a second lens holder and asecond lens mounted to the second lens holder. The first lens holder ismounted to the second lens holder, and the first lens is aligned withthe second lens with a surface of the first lens being in parallel witha surface of the second lens. The second lens holder includes an upperportion configured to mount the first lens holder, and a lower portionconfigured to mount the second lens. The optical device also includes adisplay and a base cover configured to mount the display. The base coveris mounted to the second lens holder of the optical assembly.

Other aspects of the present disclosure can be understood by thoseskilled in the art in light of the description, the claims, and thedrawings of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are provided for illustrative purposes accordingto various disclosed embodiments and are not intended to limit the scopeof the present disclosure.

FIG. 1 illustrates a schematic diagram of a polarization sensitiveoptical assembly;

FIG. 2 illustrates a schematic diagram of a fully automated assemblingand testing system;

FIG. 3 illustrates a plurality of sub-systems included in the fullyautomated assembling and testing system of FIG. 2;

FIG. 4 is a flow chart illustrating a method for assembling and testinga plurality of lens;

FIG. 5 is a flow chart illustrating example steps that may be includedin step 430 of the method shown in FIG. 4;

FIG. 6 is a flow chart illustrating a method for processing a pluralityof lens in a second assembly and validation line;

FIG. 7 is a perspective front view of an example second lens holderconfigured for mounting a second lens;

FIG. 8 is a perspective back view of the second lens holder shown inFIG. 7;

FIG. 9A is an exploded side view of a first lens holder configured formounting a first lens;

FIG. 9B is an exploded perspective view of the first lens holder shownin FIG. 9A;

FIG. 10 is a schematic illustration of a top cross-sectional view of afirst member included in the first lens holder with the first lensmounted thereon;

FIG. 11 is a perspective view of a portion of a rotation stage with thesecond lens holder mounted thereon;

FIG. 12 is a top view of the second lens holder mounted on the rotationstage;

FIG. 13 is a side view of the first lens holder mounted to a rotationstage;

FIG. 14 is a top view of the first lens holder mounted to a rotationstage;

FIG. 15 is a perspective view of the second lens holder and the firstlens holder mounted to a rotation stage;

FIG. 16 is a side view showing two rotation stages aligned together;

FIG. 17 is a side view of the first lens holder coupled to the secondlens holder after a rotation stage is separated from the first lensholder;

FIG. 18 is a perspective view of an assembly of the first lens holderand the second lens holder, after the rotation stages are removed;

FIG. 19 is a perspective view of the second lens holder mounted to arotation stage, with the first lens holder coupled to the second lensholder;

FIG. 20 is a perspective view of an optical assembly including the firstlens holder, the first lens mounted to the first lens holder, the secondlens holder, and the second lens mounted to the second lens holder;

FIG. 21 is a top view of the optical assembly of FIG. 20;

FIG. 22 is a perspective view of two rotation stages facing each other;

FIG. 23 is another perspective view the two rotation stages;

FIG. 24 is a perspective view showing a display attached to the opticalassembly through a base cover;

FIG. 25 is a perspective view of an optical device including the opticalassembly and the display;

FIG. 26 is a perspective view of the optical device including theoptical assembly and the display mounted on the base cover; and

FIG. 27 is a perspective view of the base cover.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thedisclosure, which are illustrated in the accompanying drawings.Hereinafter, embodiments consistent with the disclosure will bedescribed with reference to drawings. In the drawings, the shape andsize may be exaggerated, distorted, or simplified for clarity. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts, and a detailed descriptionthereof may be omitted.

Further, in the present disclosure, the disclosed embodiments and thefeatures of the disclosed embodiments may be combined under conditionswithout conflicts. It is apparent that the described embodiments aresome but not all of the embodiments of the present disclosure. Based onthe disclosed embodiments, persons of ordinary skill in the art mayderive other embodiments consistent with the present disclosure, all ofwhich are within the scope of the present disclosure.

The present disclosure provides a system and a method for fullyautomated assembling and testing (or validating) of optical lenses. Afully automated assembling and testing system may include a firstassembly and validation line and a second assembly and validation line.Lenses are first assembled and validated in the first assembly andvalidation line. If the assembled lens structure fails the validation ortest, the assembled lens structure may be disassembled and moved to thesecond assembly and validation line for correcting at least one of acentering, a tilting, or a polarization effect (e.g., a polarimetricangle) of each of the lenses before the lenses are re-assembled.

In some embodiments, in the first assembly and validation line, a firstlens may be press-fit into a first lens holder with a tightly controlledtolerance, and a second lens may be press-fit into a second lens holderwith a tightly controlled tolerance. The first lens holder and thesecond lens holder may not include a centering or tilting adjustmentmechanism. The first lens holder and the second lens holder may becoupled together to form a first optical assembly. A display may becoupled to the first optical assembly to form an optical device. Aquality control test or validation of various optical properties may beperformed on the first optical assembly using the display. If the firstoptical assembly fails the quality control test or validation, the firstoptical assembly may be transferred to a second assembly and validationline.

At the second assembly and validation line, simultaneous assembling andalignment may be achieved. First, the display may be separated from thefirst optical assembly, and the first optical assembly may be furtherdisassembled (alternatively, the first optical assembly may bedisassembled before moving to the second assembly and validation line)into individual pieces (e.g., first lens, second lens). Each of thefirst lens and the second lens may be placed into a respective lensholder that may include one or more mechanisms configured to adjust theorientation and/or position of the lens (e.g., centering and/or tiltingof the lens). Each of the first lens and the second lens may beseparately tested or measured for at least one of centering, tilting, ora polarization effect. When the measurement does not satisfy apredetermined condition relating to centering, tilting, or polarizationeffect, each of the first lens and the second lens may be separatelyadjusted. For example, the first lens and/or the second lens may beadjusted for centering, tilting, or polarization effect (e.g., apolarimetric angle of the lens). After the one or more adjustments areperformed on the first lens and/or the second lens, the first lens andthe second lens may be assembled to form a second optical assembly. Thedisplay may be coupled with the second optical assembly and a qualitycontrol test or validation (which may include an alignment validation)may be performed to validate an alignment between the first lens and thesecond lens using the display. Based on a result of the alignmentvalidation, the first lens and the second lens may be fine-tuned ifneeded. When the result of the quality control test meets apredetermined condition, the coupling between the first lens, the secondlens, and the display may be secured to form an optical device. Theoptical device may be used in various devices, such as a head-mounteddisplay.

The fully automated assembling and testing system of the presentdisclosure first processes the optical assembly in the first assemblyand validation line. If the optical assembly fails a quality controltest, unlike the conventional systems that may discard the opticalassembly as a defective product, the disclosed fully automatedassembling and testing system transfers the failed optical assembly to asecond assembly and validation line, where the failed optical assemblyis disassembled into individual elements (e.g., first lens and secondlens), and each individual lens is tested and/or adjusted for centering,tilting, and/or polarization effect (e.g., polarimetric angle). Afterthe adjustments are performed, the first lens and the second lens may bere-assembled to form another optical assembly. The disclosed system canreduce the failure rate of the final product by processing the failedoptical assembly through the second assembly and validation line. Inaddition, the disclosed system also reduces the cycle time by fullyautomating the processing of the lenses. As a result, the disclosedsystem can reduce the overall manufacturing costs as compared toconventional systems.

FIG. 1 illustrates an example polarization sensitive optical assembly100. The polarization sensitive optical assembly 100 may be formed by atleast two optical elements (e.g., at least two optical lenses). Thepolarization sensitive optical assembly 100 may be sensitive to thealignment (e.g., polarization alignment) of the at least two opticalelements, as the polarization alignment may affect the output of thepolarization sensitive optical assembly 100. In some embodiments, thepolarization sensitive optical assembly 100 may include a pancake lens(or a pancake lens assembly) which may be used in an optical system,such as a head-mounted display (“HMD”), to fold the optical path,thereby reducing the back focal distance in the HMD. The polarizationsensitive optical assembly 100 may include a first optical element 101and a second optical element 102 arranged in optical series to directlight 140 from an electronic display 110 to an eye-box located at anexit pupil 120 and further to an eye 130. In some embodiments, the firstoptical element 101 and the second optical element 102 may be coupledtogether by an adhesive 103. Each of the first optical element 101 andthe second optical element 102 may include one or more optical lenses.For example, in some embodiments, the first optical element 101 mayinclude a lens element 105 and a quarter-wave plate 106. Thequarter-wave plate 106 may be attached or coupled to a surface (e.g., afront or back surface) of the lens element 105. In some embodiments, thequarter-wave plate 106 may be a separate film or coating attached to orcoated on the surface of the lens element 105. The second opticalelement 102 may include a lens element 115 and a reflective polarizer116. The reflective polarizer 116 may be attached or coupled to asurface (e.g., a front or back surface) of the lens element 106. In someembodiments, the reflective polarizer 116 may be a separate film orcoating attached to or coated on the surface of the lens element 106.The polarization sensitive optical assembly 100 shown in FIG. 1 ismerely for illustrative purposes, in some embodiments, the polarizationsensitive optical assembly 100 may include other optical elements, suchas a partial reflector, a polarizer, which is not limited by the presentdisclosure. Further, in the disclosed embodiments, the quarter-waveplate 106 may include a polarization axis, which may be orientedrelative to the polarization direction of the incident linearlypolarized light to convert the linearly polarized light into acircularly polarized light or vice versa for a visible spectrum and/orinfrared spectrum. In some embodiments, for an achromatic design, thequarter-wave plate 106 may include a multilayer birefringent material(e.g., polymer or liquid crystals) to produce quarter wave birefringenceacross a wide spectral range. In some embodiments, for a simplemonochrome design, an angle between the polarization axis (i.e., fastaxis) of the quarter-wave plate 106 and incident linearly polarizedlight may be approximately 45 degrees.

The reflective polarizer 116 may be a partially reflective mirrorconfigured to reflect a received light of a first linear polarizationand transmit a received light of a second linear polarization. Forexample, the reflective polarizer 116 may reflect light polarized in ablocking direction (e.g., x-axis direction), and transmit lightpolarized in a perpendicular direction (e.g., y-axis direction). In thedisclosed embodiments, the blocking direction is referred as a directionof a blocking axis or a blocking axis direction of the reflectivepolarizer 116, and the perpendicular direction is referred as adirection of a transmission axis or a transmission axis direction of thereflective polarizer 116.

The polarization sensitive optical assembly 100 may be polarizationsensitive. For example, the polarization sensitive optical assembly 100may be sensitive to the polarization alignment between the quarter-waveplate included in the first optical element 101 and the reflectivepolarizer 116 included in the second optical element 102. That is, thepolarization sensitive optical assembly 100 may be sensitive to thealignment between the polarization axis of the quarter-wave plate 106included in the first optical element 101 and the transmission axisand/or the blocking axis of the reflective polarizer 116 included in thesecond optical element 102. In some embodiments, the polarizationalignment between the first optical element 101 and the second opticalelement 102 may affect the optical output of the polarization sensitiveoptical assembly 100. In some embodiments, any deviations in thepositions, orientations, and polarization alignment between the firstoptical element 101 and the second optical element 102 may affect theoptical output of the polarization sensitive optical assembly 100. Insome embodiments, if the positions, orientations, and polarizationalignment do not meet desired (or predetermined) respectivespecifications, the polarization sensitive optical assembly 100 may notachieve a desired optical property (e.g., a desired optical output). Asa result, the polarization sensitive optical assembly 100 assembled fromthe first optical element 101 and the second optical element 102 maybecome a defective product, which may be discarded and wasted inconventional assembly systems.

FIG. 2 illustrates an example fully automated assembling and testingsystem 200 according to an embodiment of the present disclosure. Thesystem 200 may include a full automation assembly line 201. Arrow 202indicates an example moving direction of the full automation assemblyline 201. The full automation assembly line 201 may include a conveyorbelt configured to convey or transfer parts from one station to another.A person having ordinary skills in the art would appreciate that thefull automation assembly line 201 is a schematic illustration only.Actual implementation of the full automation assembly line 201 may bedifferent. For example, instead of using a conveyance belt fortransferring a lens holder from one station to another in the fullautomation assembly line 201, in some embodiments, robotic arms may movethe lens holder from one station to another.

The full automation assembly line 201 may include two assembly andvalidation lines, referred to as “Bin 1” or 261 and “Bin 2” or 262. Inthe first assembly and validation line 261 (“Bin 1”), a first lens 203may be transferred by a robotic arm 204 from the conveyor belt to afirst lens holder 211. The first lens holder 211 may have a tightlycontrolled tolerance. In some embodiments, the first lens 203 may bepress-fit into the first lens holder 211. The first lens holder 211 maynot include an adjustment mechanism configured to adjust a centeringand/or a tilting of the first lens 203. Likewise, a second lens 207 maybe transferred by the robotic arm 204 to a second lens holder 212. Thesecond lens holder 212 may have a tightly controlled tolerance. In someembodiments, the second lens 207 may be press-fit into the second lensholder 212. The second lens holder 212 may not include an adjustmentmechanism for adjusting the centering and/or the tilting of the secondlens 207. At a bottom side of the first lens holder 211, a baffle 214may be provided and coupled to the first lens holder 211. Likewise, at abottom side of the second lens holder 212, a baffle 214 may be providedand coupled to the second lens holder 212. The first lens holder 211 maybe coupled with the second lens holder 212 (hence the first lens 203 maybe coupled with the second lens 207) to form a first optical assembly205. The first optical assembly 205 may be a pancake lens discussedabove, which may be sensitive to error in the positions, orientations,and/or polarization alignment of the first lens 203 and the second lens207, which may affect the final optical property of the pancake lens. Insome embodiments, the first lens holder 211 and the second lens holder212 may be aligned and coupled through the battles 214 respectivelyprovided at the bottoms of the first lens holder 211 and the second lensholder 212. FIG. 2 shows a top view of the baffle 214 and a side view ofthe baffle 214. As shown in FIG. 2, the baffle 214 may include alignmentindicators (e.g., the opposing notches). A display 206 may be coupledwith the first optical assembly 205. For example, the display 206 may becoupled to the first lens holder 211. A quality control test orvalidation 210 may be performed on the first optical assembly 205 usingthe display 206 and an image capturing device 213 (e.g., a camera)disposed at another side of the first optical assembly 205 opposite thedisplay 206 (e.g., on the second lens holder 212 side). Image lightemitted by the display 206 may travel through the first lens 203 and thesecond lens 207, and may be captured by the image capturing device 213.The quality control test or validation 210 may test or validate one ormore optical properties of the first optical assembly 205, such as analignment between the first lens 203 and the second lens 207. Forexample, the image capturing device 213 may be used to check thecontrast, ghosting on various patterns produced in the display 206 tovalidate the alignment.

If the first optical assembly 205 fails the quality control test orvalidation 210, the first optical assembly 205 may be transferred to thesecond assembly and validation line 262, indicated by “Bin 2,” where thefirst optical assembly 205 may be disassembled and each individual lensmay be tested and adjusted before they are re-assembled to form a secondoptical assembly. If the first optical assembly 205 passes the qualitycontrol test or validation 210, the coupling between the first opticalassembly 205 and the display 206 may be secured to form a final opticaldevice.

In the second assembly and validation line 262 (“Bin 2”), thedisassembled lens (e.g., first lens 203) may be placed in a first lensholder 217 provided in the second assembly and validation line 262. Thefirst lens holder 217 provided in the second assembly and validationline 262 may include at least one of a centering or a tilting adjustmentmechanism configured to adjust at least one of a position (e.g.,centering) or an orientation (e.g., tilting) of the first lens 203. Insome embodiments, the first lens holder 217 may include both a centeringadjustment mechanism and a tilting adjustment mechanism. The centeringadjustment mechanism may be configured to adjust a horizontal (orcentering) position of a lens (e.g., first lens 203) disposed in thefirst lens holder 217 such that the lens is located at a center location(e.g., a rotation center) of the first lens holder 217. The centeringadjustment mechanism may include a spring 215 and a set screw 216, asshown in FIG. 2. A person having ordinary skills in the art wouldappreciate that the centering adjustment mechanism may include more thanone spring and more than one set screw (e.g., three pairs of spring andscrew), or no spring. In some embodiments, the centering adjustmentmechanism may include other suitable mechanism other than the springand/or screw shown in FIG. 2. The tilting adjustment mechanism may beconfigured to adjust the orientation of the lens (e.g., tilting of thelens). The tilting adjustment mechanism may include a spring 231 and ascrew 232 having a wedge-shaped head. A person having ordinary skills inthe art would appreciate that the spring 232 and the screw 232 are onlyexamples of the tilting adjustment mechanism. Any other suitable tiltingadjustment mechanism may be used. In some embodiments, the centeringadjustment mechanism and the tilting adjustment mechanism may notinclude a spring.

The baffle 214 may be coupled to a bottom of the first lens holder 217to form a lens cell 218. The lens cell 218 may be placed onto a conveyorbelt of the full automation assembly line 201, which may convey ortransfer the lens cell 218 to a plurality of stations for processing. Aperson having ordinary skills in the art would appreciate that thesystem 200 may include one or more robotic arms to transfer the lenscell 218 to different stations, rather than using a conveyor belt. Othermethods or systems for transferring the lens cells 218 to differentstations may also be used.

Although FIG. 2 only shows the processing of the first lens 203 in thesecond assembly and validation line 262 (“Bin 2”), it is understood thatthe second lens 207 may be processed similarly. For example, the secondlens 207 may be disassembled from the second lens holder 212 of thefirst optical assembly 205. The second lens 207 may be placed into asecond lens holder 227 provided in the second assembly and validationline 262. The second lens holder 227 may be different from the secondlens holder 212 provided in the first assembly and validation line 261.The second lens holder 227 may be structurally similar to the first lensholder 217, which may include at least one of a centering or a tiltingadjustment mechanism (e.g., both a centering mechanism and a tiltingadjustment mechanism) configured to adjust a position (e.g., centering)and/or an orientation (e.g., tilting) of the second lens 207. A baffle214 may be coupled to a bottom of the second lens holder 227 to form alens cell similar to the lens cell 218. Similar to the lens cell 218,the lens cell formed by the second lens 207 and the second lens holder227 may be transferred to different stations for processing using aconveyor belt or a robotic arm included in the system 200. In otherwords, the first lens 203 and the second lens 207 may be separatelyplaced in a lens holder, and may be separately processed in variousstations. At the various stations of the second assembly and validationline, a position (e.g., centering position) and/or orientation (e.g.,tilting) of the first lens 203 and the second lens 207 in the respectivelens holder may be measured. If the position and/or orientation are notat the desired position and/or orientation (e.g., based on a measuredoptical property), the position and/or orientation of each individuallens may be adjusted using the centering mechanism and/or the tiltingmechanism. In addition, the polarization effect of the individual lensmay be separately adjusted to achieve a desired polarization effect.

As shown in FIG. 2, the first lens cell 218 (including the first lens203) may be processed at various stations. At Station 1 and Station 2,an optical center measurement may be performed. The optical centermeasurement may include at least one of a centering measurement or atilting measurement. The centering measurement measures whether the lensis located at a center location with respect to the lens holder. Thetilting measurement measures whether the lens is horizontal (or istilted) with respect to a testing light incident on the lens. If theoptical center measurement does not satisfy a predetermined opticalcenter condition, an optical center adjustment may be performed. Thepredetermined optical center condition may include at least one of apredetermined centering condition or a predetermined tilting condition.The optical center adjustment may include at least one of a centeringadjustment or a tilting adjustment.

At Station 3 and Station 4, a polarimetric measurement or a polarizationvalidation may be performed. The polarimetric measurement may indicate apolarization effect of the lens, i.e., a polarization state of the lighttransmitted through the lens given an incident light with a specificpolarization state. If the polarimetric measurement does not satisfy apredetermined polarimetric condition, a polarimetric angle adjustmentmay be performed on the lens. Depending on the type of optical elementincluded in the lens that may affect the polarization effect of thelens, different polarimetric measurements and polarimetric angleadjustments may be performed. For example, if the lens includes aquarter-wave plate that may affect the polarization effect of the lens,the polarimetric measurement may include a measurement relating to apolarization effect of the quarter-wave plate. Performing thepolarimetric angle adjustment may include performing a quarter-waveplate angle adjustment when the measurement does not satisfy apredetermined condition relating to the polarization effect of thequarter-wave plate. In particular, performing the quarter-wave plateangle adjustment may include rotating the lens including thequarter-wave plate to produce a desired polarization effect, i.e., adesired polarization state of the light transmitted through the lensgiven a specifically polarized incident light. For example, thepolarization axis of the quarter-wave plate may be oriented relative tothe polarization direction of the incident linearly polarized light toconvert the linearly polarized light into circularly polarized light orvice versa. If the lens includes a reflective polarizer, thepolarimetric measurement may include a measurement relating to apolarization effect of the reflective polarizer. Performing thepolarimetric angle adjustment may include performing a reflectivepolarizer angle adjustment when the measurement does not satisfy apredetermined condition relating to the polarization effect of thereflective polarizer. In particular, performing the reflective polarizerangle adjustment may include rotating the lens including the reflectivepolarizer to produce a desired polarization effect, i.e., a desiredpolarization state of the light transmitted through the lens given aspecifically polarized incident light. For example, the transmissionaxis (or blocking axis) of the reflective polarizer may be orientedrelative to the polarization direction of the incident linearlypolarized light to completely transmit (or block) the incident linearlypolarized light. In some embodiments, Station 3 and Station 4 may be twoseparate stations along the second assembly and validation line 262,each processing a lens holder (e.g., Station 3 processing the first lensholder 217 with the first lens 203 and Station 4 processing the secondlens holder 227 with the second lens 207). In some embodiments, Station3 and Station 4 may be the same station for processing the first lensholder 217 (hence the first lens 203) and the second lens holder 227(hence the second lens 207). When one lens holder is processed, thatlens holder may be moved out of the station such that another lensholder may be moved in and processed at the station.

Referring to FIG. 2, the first lens 203 may be processed at Station 1for measuring and/or adjusting the position (e.g., centering) of thefirst lens 203. For example, at Station 1, a centering measurement ofthe first lens 203 indicating whether the first lens 203 is disposed ata center location in the first lens holder 217 may be performed. If thecentering measurement does not satisfy a predetermined centeringcondition, a centering adjustment (also referred to as a decenteringcorrection) may be performed on the first lens 203 using the centeringadjustment mechanism provided in the first lens holder 217 until thecentering measurement satisfies the predetermined centering condition.For example, the centering of the first lens 203 may be adjusted byadjusting the screw 216. If the centering measurement initiallyperformed satisfies the predetermined centering condition, no centeringadjustment will be performed. It is understood that a similar processmay be performed on the second lens 207.

After the centering measurement and adjustment (if needed) areperformed, the lens cell 218 may be transferred to a Station 2. AtStation 2, a tilting measurement for the first lens 203 may beperformed. When the tilting measurement satisfies a predeterminedtilting condition, no tilting adjustment will be performed. When thetilting measurement does not satisfy the predetermined tiltingcondition, a tilting adjustment (also referred to as a tiltingcorrection) may be performed on the first lens 203 using the tiltingadjustment mechanism provided on the first lens holder 217. For example,the tilting adjustment may be performed by adjusting the screw 232having a wedge-shaped head to change the tilting of the first lens 203.It is understood that a similar process may be performed on the secondlens 207.

It is understood that in some embodiments, the centering measurement andadjustment may be performed after the tilting measurement and adjustmentare performed. In some embodiments, at least one of the first lensholder 217 or the second lens holder 227 may not include a centeringadjustment mechanism. For example, the first lens holder 217 may notinclude a centering adjustment mechanism. The centering location of thefirst lens 203 may serve as the reference for the second lens 207, andcentering of the second lens 207 may be adjusted to match that of thefirst lens 203. Likewise, in some embodiments, the second lens holder227 may not include a centering adjustment mechanism. The centeringlocation of the second lens 207 may serve as the reference for the firstlens 203, and the centering of the first lens 203 may be adjusted tomatch that of the second lens 207. In some embodiments, at least one ofthe first lens holder 217 or the second lens holder 227 may not includea tilting adjustment mechanism. For example, the first lens holder 227may not include a tilting adjustment mechanism, and the orientation(e.g., tilting angle) of the first lens 203 may serve as a reference.The second lens 207 may be adjusted for its tilting to match that of thefirst lens 203 (e.g., such that the second lens 207 is substantiallyparallel with the first lens 203). Likewise, in some embodiments, thesecond lens holder 227 may not include a tilting mechanism. Theorientation (e.g., tilting angle) of the second lens 207 may serve as areference for the first lens 203. The tilting of the first lens 203 maybe adjusted to match that of the second lens 207 (e.g., such that thefirst lens 203 is substantially parallel with the second lens 207).

In some embodiments, the first lens holder 217 and the second lensholder 227 may each include both the centering adjustment mechanism andthe tilting adjustment mechanism. However, at Station 1 and Station 2,not every lens (first lens 203 and second lens 207) is adjusted for itscentering or tilting. In other words, centering measurement andadjustment or tilting measurement and adjustment may be omitted for thefirst lens 203 or the second lens 207, for example, for reasonsdiscussed above relating to the first lens 203 or the second lens 207being a reference for the other one.

In some embodiments, after the centering and/or tilting measurement andadjustment are performed, the lens cell 218 may be transferred to aStation 3. For illustrative purposes, it is assumed that the first lens203 includes a quarter-wave plate that may affect the polarizationeffect of the first lens 203, and the second lens 207 includes areflective polarizer that may affect the polarization effect of thesecond lens 207. At Station 3, a measurement relating to a polarizationeffect of a quarter-wave plate included in the first lens 203 may beperformed. If the measurement satisfies a predetermined conditionrelating to the polarization effect of the quarter-wave plate, nopolarimetric angle adjustment will be performed. If the measurement doesnot satisfy a predetermined condition relating to the polarizationeffect of the quarter-wave plate, a polarimetric angle adjustment may beperformed for the first lens 203. The polarimetric angle of thequarter-wave plate may be adjusted until the measurement relating to thepolarization effect of the quarter-wave plate satisfies thepredetermined condition relating to the polarization effect of thequarter-wave plate.

The lens cell formed by the second lens 207 and the second lens holder227 may be transferred to a Station 4 after the centering and/or tiltingmeasurement and adjustment are performed. At Station 4, a measurementrelating to a polarization effect of the reflective polarizer includedin second lens 207 is performed. If the measurement satisfies apredetermined condition relating to the polarization effect of thereflective polarizer, no polarimetric angle adjustment will beperformed. If the measurement does not satisfy the predeterminedcondition relating to the polarization effect of the reflectivepolarizer, a reflective polarizer angle adjustment may be performed forthe second lens 207 until the measurement satisfies the predeterminedcondition relating to the polarization effect of the reflectivepolarizer. It is understood that the lens cell formed by the second lens207 and the second lens holder 227 may not be transferred to Station 3before being transferred to Station 4. Rather, the lens cell may bedirectly transferred from Station 1 or Station 2.

Both the lens cell formed by the first lens 203 and the first lensholder 217 and the lens cell formed by the second lens 207 and thesecond lens holder 227 may be transferred to a Station 5, where they areassembled together (hence the first lens 203 and the second lens 207 areassembled) to form a second optical assembly. For example, the firstlens holder 217 and the second lens holder 227 may be aligned andcoupled together using the baffle 214 attached to the bottoms of thefirst lens holder 217 and the second lens holder 227. The display 206may be coupled with the second optical assembly. A quality control testor validation 225, which may be similar to the quality control test orvalidation 210 performed at Bin 1 may be performed to validate thealignment (e.g., polarization alignment, optical axis alignment) betweenthe first lens 203 and the second lens 207. The quality control test orvalidation 225 may be performed using the display 206 and an imagecapturing device 219, such as a camera 219. If the second opticalassembly passes the quality control test or validation 225, the couplingbetween the display 206 and the second optical assembly may be securedto form an optical device. For example, the first lens holder 227 andthe second lens holder 227 may be glued together using an ultraviolet(“UV”) cured glue, or may be coupled together using any other methods,such as screws, clamps, etc. If the second optical assembly does notpass the quality control test or validation 225, fine-tuning oradjustment of the alignment between the first lens 203 and the secondlens 207 may be performed until the second optical assembly passes thequality control test or validation 225.

FIG. 3 illustrates a plurality of sub-systems included in the fullyautomated assembling and testing system 200. Specifically, thesub-systems are included in the second assembly and validation line 262shown in FIG. 2. Various stations are shown in FIG. 2 and describedabove briefly. FIG. 3 shows additional details of the various stations.

As shown in FIG. 3, the second assembly and validation line 262 mayinclude a first sub-system 381, a second sub-system 382, and a thirdsub-system 383. The first sub-system 381 may be configured to perform anoptical center measurement for at least one of the first lens or thesecond lens, and perform an optical center adjustment when the opticalcenter measurement does not satisfy a predetermined optical centercondition. As discussed above, the optical center measurement mayinclude a centering measurement and a tilting measurement. The opticalcenter adjustment may include a centering adjustment and a tiltingadjustment. The predetermined optical center condition may include apredetermined centering condition and a predetermined tilting condition.Correspondingly, the first sub-system 381 may include Station 1configured to perform the centering measurement and the centeringadjustment, and Station 2 configured to perform the tilting measurementand the tilting adjustment.

The first sub-system 381 may include at least one of a laser emitter andan image capturing device. For example, as shown in FIG. 3, Station 1may include a laser emitter 311 and an image capturing device 351 (e.g.,camera). Station 2 may include a laser emitter 312 and a first imagecapturing device 352 (e.g., camera) and a second image capturing device353 (e.g., camera). Station 1 may also include a first iris 371 and asecond iris 372. Likewise, Station 2 may include a first iris 373 and asecond iris 374.

At Station 1, a centering measurement and/or a centering adjustment maybe performed for a lens, such as the first lens 302 and the second lens307, respectively. For illustrative purposes, only the first lens 302 isshown at Station 1 and Station 2. It is understood that similarprocesses performed at Stations 1 and 2 for the first lens 302 may beperformed on the second lens 307.

Station 1 may include a rotation stage 330 configured to hold and rotatea lens holder containing a lens (e.g., the first lens holder 217containing the first lens 203). When performing a centering measurementand centering adjustment, the lens may be rotated as the centeringmeasurement and/or adjustment are performed. The laser emitter 311 mayemit a laser beam 321. The laser beam 321 may pass through the firstiris 371 and pass through the second iris 372 when there is no opticalelement on the optical path of the laser beam 321. When the first lensholder 217 with the first lens 203 disposed therein is placed betweenthe first iris 371 and the second iris 372, the optical path of thelaser beam 321 may be altered or affected by the first lens 203. Aportion of the laser beam 321 transmitted through the first lens 203 mayarrive at the second iris 372. When the first lens 203 is not at thecenter position (e.g., when the optical axis of the first lens 203 isnot parallel with the laser beam 321), the portion of the laser beam 321transmitted through the first lens 203 may deviate from the originallaser beam. In other words, the portion of the laser beam 321transmitted through the first lens 203 may deviate from the second iris372.

The image capturing device 351 may capture images of the laser beam 321and the second iris 372 as the rotation stage 330 rotates 360°, causingthe first lens 203 to rotate 360°. The images captured as the first lens203 is rotated from 0 to 360° may indicate whether the laser beam 321wobbles around the second iris 372 or whether the laser beam 321propagates through the second iris 372 all the time as the first lens203 is rotated. A person having ordinary skills in the art wouldappreciate that in some embodiments, the rotation stage 330 may not needto rotate 360°, but rather may only rotate from 0 to a suitable angleless than 360° (e.g., 180°, 250°, etc.). Capturing the images may be anembodiment of performing a centering measurement. The images captured bythe image capturing device 351 may be processed by a processor (notshown) to determine whether the first lens 203 is at the centerposition. For example, the processor may analyze the images anddetermine whether the laser beam 321 propagates or travels through thesecond iris 372, or whether the laser beam 321 wobbles around the iris372. An embodiment of a predetermined centering condition may be thelaser beam 321 traveling through the second iris 372. When the imageindicates that the laser beam 321 travels through the second iris 372,it means that the centering measurement satisfies the predeterminedcentering condition. When the image indicates that the laser beam 321wobbles around the second iris 372, it means that the centeringmeasurement does not satisfy the predetermined centering condition.

Based on a determination that the laser beam 321 does not travel throughthe second iris 372 (i.e., wobbles around the second iris 372), theprocessor may provide a command to an automated tool (not shown) toinstruct the automated tool to adjust the centering mechanism. When thecentering mechanism includes a screw configured to adjust the centeringposition of the first lens 203, the automated tool may include acorresponding screw adjusting tool (e.g., a screw driver). The commandmay instruct the automated tool to adjust the centering mechanism (e.g.,the screw 216) for a certain amount to correct the centering position ofthe first lens 203. After the centering mechanism is adjusted or whilethe centering mechanism is adjusted, images of the laser beam 321 andthe second iris 372 may be captured by the image capturing device 351,and analyzed by the processor to determine whether the adjustment of thecentering mechanism has placed the first lens 203 at a center position(e.g., by determining whether the laser beam 321 travels through thesecond iris 372 rather than wobbles around the second iris 372).

Thus, in some embodiments, a closed-loop feedback system may be formedby the processor, the image capturing device 351, and the automated toolconfigured to adjust the centering mechanism. The image informationcaptured by the image capturing device 351 may be used to generate afeedback to control the automated tool to adjust the centeringmechanism. The control and the adjustment may be automatically performeduntil the image captured by the image capturing device 351 indicatesthat the portion of the laser beam 321 transmitted through the firstlens 203 does not wobble around the second iris 372, but instead,travels through the second iris 372. At this state, the processor maydetermine that the first lens 203 is at a center position (i.e., thecentering measurement satisfies the predetermined centering condition).

In some embodiments, after the centering measurement and adjustment areperformed on the first lens 203, the first lens 203 may be transferredto Station 2. It is understood that in some embodiments, the first lens203 (or the second lens 207) may not need go through Station 1 orStation 2. At Station 2, a tilting measurement and/or adjustment may beperformed on the first lens 203. Station 2 may include a laser emitter312 configured to emit a laser beam 322. Station 2 may include a firstiris 373 and a second iris 374. The laser beam 322 may travel throughthe first iris 373 and the second iris 374 when there is no otheroptical element disposed between the first iris 373 and the second iris374 (e.g., when the first lens 203 is not located between the first iris373 and the second iris 374). Station 2 may include a first imagecapturing device 352 and a second image capturing device 353. The firstimage capturing device 352 and the second image capturing device 353 maybe cameras. The first image capturing device 352 may be configured tocapture images of a portion of the laser beam 322 transmitted throughthe first lens 203 and the second iris 374, which may indicate therelative positions of the portion of the laser beam 322 and the secondiris 374 (e.g., whether the portion of the laser beam 322 travelsthrough the second iris 374 or whether the portion of the laser beam 322wobbles around the second iris 374). The second image capturing device353 may be configured to capture images of a portion of the laser beam322 reflected by the first lens 203 and the first iris 373, which mayindicate the relative positions of the portion of the laser beam 322reflected by the first lens 203 and the first iris 373 (e.g., whetherthe reflected laser beam travels through the first iris 373 or whetherthe reflected laser beam wobbles around the first iris 373).

Station 2 may also include a rotation stage 335 configured to hold androtate the first lens holder 217 to cause the first lens 203 to rotate.The first lens holder 217 may include a tilting adjustment mechanism.The tilting adjustment mechanism may include at least one screw 317having a wedge-shaped head. FIG. 3 shows the tilting adjustmentmechanism having two screws 317 having a wedge-shaped head. A personhaving ordinary skills in the art would appreciate that the schematicillustration of the first lens holder 217 is only one embodiment. Insome embodiments, as shown in FIG. 2, the first lens holder 217 mayinclude at least one spring (which may be similar to spring 231). Insome embodiments, other suitable tilting adjustment mechanism may beincluded in the first lens holder 217.

A tilting measurement may be performed at Station 2. In someembodiments, the tilting measurement may be performed by the secondimage capturing device 353. The second image capturing device 353 maycapture images of the portion of the laser beam 322 reflected by thefirst lens 203 back to the first iris 373, and the first iris 373. Whenthe reflected portion of the laser beam 322 travels through the firstiris 373, or when the reflected portion of the laser beam 322 wobbleswithin a predetermined range around the first iris 373, as the firstlens 203 is rotated 360° by the rotation stage 335, the processor maydetermine that the tilting measurement satisfies a predetermined tiltingcondition. A person having ordinary skills in the art would appreciatethat in some embodiments, the rotation stage 335 may not need to rotate360°, but rather may only rotate from 0° to a suitable angle less than360°. The predetermined tilting condition may be that the reflectedportion of the laser beam 322 wobbles within a predetermined rangearound the first iris 373. The predetermined range may be any suitablerange determined based on a desired specification. For example, thepredetermined range may be 1 mm laser beam diameter at 0.5 meter awayfrom the first lens 203 (or approximately 2 milliradian (“mrad”), or0.11°). Thus, in some embodiments, when the reflected portion of thelaser beam 322 wobbles within approximately 1 mm laser beam diameter at0.5 m away from the first lens 203, the predetermined tilting conditionis deemed satisfied, and no further tilting correction will beperformed. If the tilting measurement indicates that the reflectedportion of the laser beam 322 wobbles outside of the predetermined range(e.g., greater than 1 mm laser beam diameter at 0.5 m away from thefirst lens 203), the processor may determine that tilting correction oradjustment needs to be performed on the first lens 203. The processormay determine an amount of tilting adjustment needed and may provide afeedback control signal to an automated tool (not shown) configured toadjust the tilting adjustment mechanism. The tilting adjustment andmeasurement may be repeated until the tilting measurement satisfies thepredetermined tilting condition. It is understood that similar processesmay be performed on the second lens 207 separately.

After the tilting measurement and adjustment are performed, a lens maybe transferred to Station 3 or Station 4, where a polarimetricmeasurement and/or a polarimetric angle adjustment may be performed onthe lens. The polarimetric angle adjustment may be performed on the lenswhen the polarimetric measurement does not satisfy a predeterminedpolarimetric condition. For example, for the first lens 203, after thetilting measurement and adjustment are performed, the first lens 203 maybe transferred to Station 3, where a measurement relating to apolarization effect of a quarter-wave plate included in the first lens203 may be performed. The processor may determine whether themeasurement satisfies a predetermined condition relating to thepolarization effect of the quarter-wave plate. If the measurementsatisfies the predetermined condition relating to the polarizationeffect of the quarter-wave plate, no polarimetric angle adjustment willbe performed. If the measurement does not satisfy the predeterminedcondition relating to the polarization effect of the quarter-wave plate,a polarimetric angle adjustment (e.g., a quarter-wave plate angleadjustment) may be performed for the first lens 203.

Station 3 may include a laser emitter 313 configured to emit a laserbeam 323. Station 3 may also include an iris 375. The laser beam 323emitted by the laser emitter 313 may travel through the iris 375.Optionally, in some embodiments, Station 3 may include a linearpolarizer 361 configured to linearly polarize the emitted laser beam 323such that the laser beam 323 output from the polarizer 361 may beconfigured to have a specific polarization direction, i.e., apolarization direction along the transmission axis of the linearpolarizer 361. Station 3 may include a rotation stage 340 configured tohold and rotate the first lens holder 217 (and hence to rotate the firstlens 203). Station 3 may include an analyzer 360, which may be disposedafter the first lens 203 (i.e., downstream of the first lens 203 in theoptical path of the laser beam 323). The analyzer 360 may be a linearpolarizer having a transmission axis and a blocking axis perpendicularto the transmission axis. The analyzer 360 may be configured to transmita light having a polarization direction parallel with the transmissionaxis, and block a light having a polarization direction perpendicular tothe transmission axis (e.g., parallel with the blocking axis). Station 3may further include a power meter 365 configured to measure an intensityor transmitted power of the laser beam 323 transmitted through the firstlens 203 and the analyzer 360.

The polarimetric measurement for the first lens 203 including aquarter-wave plate (or a measurement relating to the polarization effectof the quarter-wave plate) may be conducted as follows. The rotationstage 340 may be rotated to a first angle (hence the first lens 203 orthe quarter-wave plate included in the first lens 203 is at the firstangle) with respect to the transmission axis of the linear polarizer361. The angle may also be referred to as a quarter-wave plate angle.While the first lens is at the first angle, the analyzer 360 may berotated 360°, and the intensities or transmitted powers of the portionof the laser beam 323 transmitted through the first lens 203 and theanalyzer 360 may be measured by the power meter 365 at each angle of theanalyzer 360. A person having ordinary skills in the art wouldappreciate that in some embodiments, the analyzer 360 may not need torotate 360°, but rather may only rotate from 0° to a suitable angle lessthan 360°. The intensities or transmitted powers corresponding to thedifferent angles of the analyzer 360 may be recorded. The intensities ortransmitted powers measurement may be an embodiment of the measurementrelating to a polarization effect of the quarter-wave plate included inthe first lens 203. The processor may analyze the intensities ortransmitted powers to determine whether the intensities or transmittedpowers are constant or nearly constant at different analyzer angles. Themeasured intensities or transmitted powers being constant or nearlyconstant may be an example of the predetermined condition relating tothe polarization effect of the quarter-wave plate. Various data analysismethods may be used to determine whether the intensities are constant ornearly constant. For example, if a ratio between a maximum intensity anda minimum intensity is smaller than a predetermined value, theintensities may be determined to be constant or nearly constant. Asanother example, the standard deviation of the measured intensities ortransmitted powers may be calculated. If the standard deviation issmaller than a predetermined value, the intensities or the transmittedpowers may be determined to be constant or nearly constant.

Other suitable methods may also be used to verify the polarization stateof the first lens 203. For example, an off-the-shelf polarimeter may beused to determine the polarization state of the quarter-wave plateincluded in the first lens 203.

The rotation stage 340 may continue to rotate the first lens 203 to asecond angle, and similar measurement of the intensities or transmittedpowers may be obtained and analyzed as the analyzer 360 rotates 360°.This process may be repeated until the rotation stage 340 has rotated360°. A person having ordinary skills in the art would appreciate thatin some embodiments, the rotation stage 340 may not need to rotate 360°,but rather may only rotate from 0° to a suitable angle less than 360°.When the first lens 203 is at a certain angle, a portion of the laserbeam 323 entering the first lens 203 may be converted into a circularlypolarized laser beam by the first lens 203. The circularly polarizedlaser beam output from the first lens 203, after traveling through theanalyzer 360, may become a laser beam having a constant intensity ortransmitted power regardless of the angle of the analyzer 360. Thus, themeasured intensities may be constant or nearly constant when the firstlens 203 generates a circularly polarized laser beam. When the laserbeam output from the first lens 203 is not a circularly polarized beam,the intensities measured by the power meter 365 may not be constant andmay oscillate in a sine or cosine wave shape. For example, the ratiobetween the maximum intensity and the minimum intensity may be greaterthan a predetermined value, or the standard deviation of the intensitiescorresponding to different analyzer angles may be greater than apredetermined value. The angle of the first lens 203 at which acircularly polarized beam is generated by the first lens 203 may berecorded. A baffle (which may be similar to baffle 214) may be securelycoupled to the first lens holder 217 to lock the angle of the first lens203 (also referred as a clocking angle of the first lens 203).

After the centering and/or tilting measurement and adjustment areperformed on the second lens 207 having a reflective polarizer, thesecond lens 207 may be transferred to Station 4. At Station 4, ameasurement relating to a polarization effect of a reflective polarizerincluded in the second lens 207 may be performed. Station 4 may includea laser emitter 314 configured to emit a laser beam 324. Station 4 mayinclude an iris 376. The laser beam 324 emitted by the laser emitter 314may travel through the iris 376. Station 4 may include a polarizer 362disposed upstream (in the optical path of the laser beam 324) of arotation stage 345 holding and rotating the second lens holder 227 thatcontains the second lens 207. The polarizer may be optional. Station 4may include a power meter 370, which may be similar to the power meter365.

The polarimetric measurement and polarimetric angle adjustment performedat Station 4 may be similar to those performed in Station 3. At Station4, the polarimetric measurement may be the measurement relating to apolarization effect of a reflective polarizer included in the secondlens 207. Specifically, in some embodiments, the rotation stage 345 maybe rotated to a first angle (hence the second lens 207 is at the firstangle) with respect to the transmission axis of the polarizer 362. Theangle of the second lens 207 may also be referred to as a reflectivepolarizer angle. At each lens angle, the intensity or transmitted powerof the portion of the laser beam 324 transmitted through the second lens207 (which includes a reflective polarizer) may be measured by the powermeter 370. The second lens 207 may be rotated to a second angle, and theintensity or transmitted power may be recorded again. The process may berepeated until the rotation stage 345 has rotated 360°. It is understoodthat the rotation stage 345 may not need to rotate 360°. In someembodiments, the rotation stage 345 may only rotate to an angle lessthan 360°, such as 180°, 200°, 250°, etc. The measurement of theintensities may be an example of the measurement relating to apolarization effect of the reflective polarizer included in the secondlens 207. The processor may determine whether the measurement satisfiesa predetermined condition relating to the polarization effect of thereflective polarizer. In some embodiments, the transmission axis of thereflective polarizer may be orientated relative to the polarization axisof the linearly polarized light incident onto the second lens 207 (whichincludes a reflective polarizer), where the predetermined conditionrelating to the polarization effect of the reflective polarizer mayinclude, for example, a minimum transmission power among thetransmission powers measured as the second lens 207 is rotated within arange of angles. The minimum transmission power may be determined andthe corresponding angle of the second lens 207 may be recorded. A baffle214 may be securely coupled (e.g., glued) to the bottom portion of thesecond lens holder 227 to lock the reflective polarizer angle of thesecond lens 207.

After the first lens 203 is processed at Station 3 and the second lens207 is processed at Station 4, the first lens holder 217 and the secondlens holder 227 may be transferred to Station 5. At Station 5, the firstlens holder 217 and the second lens holder 227 may be aligned andcoupled together to form an optical assembly, thereby achieving adesired polarization effect of the formed optical assembly. Inparticular, each of the first lens holder 217 and the second lens holder227 may include a baffle 214 attached to the bottom portion. The baffles214 may be used to align the first lens holder 217 and the second lensholder 227 using the notches provided on the baffles 214. Referencenumber 350 indicates a rotation stage. It is understood that Station 5may include two rotation stages 350, each holding a lens holder.Rotation stage 350 may include vacuum tubings to hold the baffle 214provided at the bottom of the lens holder through vacuum forces. Withthe rotation stages 350 holding the lens holders (e.g., first lensholder 217 and second lens holder 227), the first lens 203 and thesecond lens 207 may be translated toward one another. In someembodiments, the first lens holder 217 may be coupled with the secondlens holder 227 and aligned with the second lens holder 227 using thebaffles 214. The first lens holder 217 and the second lens holder 227may form a second optical assembly. In some embodiments, the lightincident onto the second optical assembly may be circularly polarizedlight, and the first lens holder 217 may be aligned with the second lensholder 227 to not only fold the optical path but also convert thecircularly polarized light into a linearly polarized light. In someembodiments, the light incident onto the second optical assembly may belinearly polarized light with a first polarization direction, and thefirst lens holder 217 may be aligned with the second lens holder 227 tonot only fold the optical path but also convert the linearly polarizedlight with the first polarization direction into a linearly polarizedlight with a second polarization direction perpendicular to the firstpolarization direction.

Further, the display 206 may be coupled to the second optical assembly.A quality control test or validation similar to that performed at Bin 1may be performed on the second optical assembly. For example, thedisplay 206 and an image capturing device 354 (e.g., camera) may be usedto validate the alignment of the first lens 203 and the second lens 207.Various methods may be used to validate the alignment. For example, theprocessor may examine the contrast and/or ghosting features of images ofvarious patterns generated by the display 206, as captured by the imagecapturing device 354. Fine-tuning of the alignment of the first lens 203and the second lens 207 may be performed until a desired alignment isachieved. For example, in some embodiments, the fine-tuning of thealignment may be performed until the see-through ghost effect isminimized. When the alignment is confirmed, the first lens holder 217may be securely coupled with the second lens holder 227. The first lensholder 217 may be disengaged from the rotation stage 350. The display206 may be securely coupled with the first lens holder 217 or the secondlens holder 227. The second lens holder 227 may be disengaged from therotation stage 350. The final optical device may include the display206, the first lens 203 (held by at least a portion of the first lensholder 217), and the second lens 207 (held by at least a portion of thesecond lens holder 227). In some embodiments, after the first lensholder 217 and the second lens holder 227 are coupled together, aportion of the first lens holder 217 may be removed.

FIG. 4 is a flow chart illustrating a method 400 for assembling andtesting a plurality of lenses, such as the first lens 203 and the secondlens 207. Method 400 may be performed by the system 200. A person havingordinary skills in the art would appreciate that method 400 may includemore or fewer steps than those shown in FIG. 4. In addition, the orderof execution of the steps may be different from that shown in FIG. 4.Method 400 may include assembling a first lens, a second lens, and adisplay to form a first optical assembly in a first assembly andvalidation line (step 405). For example, as shown in “Bin 1” in FIG. 2,the first lens 203 and the second lens 207 may be disposed into arespective lens holder. The two lens holders may be coupled together toform a first optical assembly. Method 400 may also include testing thefirst optical assembly in the first assembly and validation line (step410). For example, a quality control test or validation may be performedon the first optical assembly using the display 206 and the imagecapturing device 213. The quality control test or validation may includeexamining the contrast and/or the ghosting effects of various patternsgenerated on the display 206, using the image capturing device 213.

Method 400 may include determining whether the first optical assemblyfails the test (step 415). If the first optical assembly passes the test(e.g., the quality control test or validation), i.e., if the testingresult satisfies a predetermined condition, the coupling between thefirst lens 203 and the second lens 207, and optionally the couplingbetween the display 206 and the first optical assembly, may be secured.In some embodiments an ultraviolet curable glue may be applied to securethe coupling between the first lens 203, the second lens 207, and/or thedisplay 206. The predetermined condition may be any suitable conditions.In some embodiments, the predetermined condition may be a predeterminedminimum amount of ghosting effect, or a predetermined contrast value. Ifthe testing result does not satisfy the predetermined condition, thefirst optical assembly may be disassembled into individual elements(e.g., first lens 203 and second lens 207) (step 415). The disassembledlenses 203 and 207 may be transferred to a second assembly andvalidation line (“Bin 2”). The first lens 203, the second lens 207, andthe display 206 may be processed in the second assembly and validationline (step 430). In some embodiments, step 425 may be part of step 430.That is, the first optical assembly may be disassembled in the secondassembly and validation line.

FIG. 5 is a flow chart illustrates a method for assembling and testingthe first lens 203 and the second lens 207 in the second assembly andvalidation line. The method may be part of the step 430. A person havingordinary skills in the art would appreciate that step 430 may includemore or fewer steps than those shown in FIG. 5. In addition, the orderof execution of the steps may be different from that shown in FIG. 5.Step 430 may include performing an optical center measurement for atleast one of the first lens 203 or the second lens 207 (step 505). Step430 may also include determining whether the optical center measurementsatisfies a predetermined optical center condition (step 510). If theoptical center measurement does not satisfy the predetermined opticalcenter condition (No, step 510), step 430 may include performing anoptical center adjustment on the lens. As discussed above, the opticalcenter measurement may include at least one of a centering measurementor a tilting measurement, and the optical center adjustment may includeat least one of a centering adjustment or a tilting adjustment. In someembodiments, the first lens 203 and the second lens 207 may each beprocessed in Station 1 and State 2 such that a centering measurement(and a centering adjustment if needed) is separately performed on thefirst lens 203 and the second lens 207, and a tilting measurement (and atilting adjustment if needed) is separately performed on the first lens203 and the second lens 207. In some embodiments, at least one of thefirst lens 203 or the second lens 207 may not be processed in Station 1or Station 2. In other words, in some embodiments, the centeringmeasurement (and the centering adjustment if needed) may not beperformed for at least one of the first lens 203 or the second lens 207.In some embodiments, the tilting measurement (and the tilting adjustmentif needed) may not be performed for at least one of the first lens 203or the second lens 207. Detailed descriptions of examples of thecentering measurement, centering adjustment, tilting measurement, andtilting adjustment may refer to the above descriptions in connectionwith FIGS. 2 and 3.

When the optical center measurement satisfies a predetermined opticalcenter condition (Yes, step 510), or after the optical center adjustmentis performed in step 515, a polarimetric measurement may be performedfor at least one of the first lens 203 or the second lens 207 (step520). As discussed above, the polarimetric measurement may include ameasurement relating to a polarization effect of a quarter-wave plate,if a quarter-wave plate is included in any of the first lens 203 and thesecond lens 207. In some embodiments, the polarimetric measurement mayinclude a measurement relating to a polarization effect of a reflectivepolarizer if the lens includes a reflective polarizer.

Step 430 may include determining whether the polarimetric measurementsatisfies a predetermined polarimetric condition (step 525). If thepolarimetric measurement does not satisfy the predetermined polarimetriccondition (No, step 525), step 430 may include performing a polarimetricangle adjustment on the lens (step 530). As discussed above inconnection with FIGS. 2 and 3, the polarimetric angle adjustment mayinclude a quarter-wave plate angle adjustment if the lens includes aquarter-wave plate, or a reflective polarizer angle adjustment if thelens includes a reflective polarizer. Detailed descriptions of examplesof steps 520, 525, and 530 may refer to the above descriptions inconnection with FIGS. 2 and 3.

After the polarimetric angle adjustment is performed, step 430 mayinclude assembling the first lens and the second lens to form a secondoptical assembly (step 535). A quality control test or validation may beperformed on the second optical assembly using a display (e.g., display206) and an image capturing device (e.g., image capturing device 354shown in FIG. 3). Detailed descriptions of examples of step 535 and thequality control test or validation may refer to the above descriptionsin connection with Station 5 shown in FIG. 3. If the second opticalassembly passes the quality control test or validation, coupling betweenthe first lens and the second lens included in the second opticalassembly may be secured. In addition, the coupling between the displayand the second optical assembly may be secured to form a final opticaldevice.

FIG. 6 is a flow chart illustrating a method for assembling and testinga first lens and a second lens. Method 600 may be performed by thesystem 200. In some embodiments, method 600 may be automaticallyperformed by the system 200. A person having ordinary skills in the artwould appreciate that method 600 may include more or fewer steps thanthose shown in FIG. 6. In addition, the order of execution of the stepsmay be different from that shown in FIG. 6. Method 600 may includeperforming a centering measurement for at least one of the first lens orthe second lens (step 605). For example, a centering measurement may beseparately performed for the first lens 203 and the second lens 207, asdiscussed above in connection with FIGS. 2 and 3. In some embodiments, acentering measurement may not be performed for one or both of the firstlens 203 and second lens 207.

Method 600 may include performing a centering adjustment when thecentering measurement does not satisfy a predetermined centeringcondition (step 610). When the centering measurement satisfies thepredetermined centering condition, the centering measurement may not beperformed. The centering adjustment may be performed by a toolconfigured to adjust a centering adjustment mechanism, such as one ormore screws provided in a lens holder. The centering measurement and thecentering adjustment may be controlled by a processor. The processor mayanalyze the centering measurement to determine whether the centeringmeasurement satisfies the predetermined centering condition. If thecentering measurement does not satisfy the predetermined centeringcondition, the processor may determine an amount of centering adjustmentneeded and may provide a command to the tool to control the tool toadjust the centering adjustment mechanism. In some embodiments, aclosed-loop control system may be formed to automatically adjust thecentering of the lens. Detailed descriptions of examples of performingthe centering adjustment may refer to the above descriptions inconnection with FIGS. 2 and 3.

Method 600 may include performing a tilting measurement for at least oneof the first lens or the second lens (step 615). For example, in someembodiments, the tilting measurement may be performed for both of thefirst lens 203 and the second lens 207 separately. In some embodiments,a tilting measurement may not be performed for one or both of the firstlens 203 and the second lens 207. Detailed descriptions of examples ofperforming the tilting measurement may refer to the above descriptionsin connection with FIGS. 2 and 3.

Method 600 may also include performing a tilting adjustment when thetilting measurement does not satisfy a predetermined tilting condition(step 620). When the tilting measurement satisfies the predeterminedtilting condition, the tilting adjustment may not be performed. Thetilting adjustment may be performed automatically by a tool configuredto adjust a tilting adjustment mechanism provided on the lens holderthat holds the lens. The processor may control the tilting measurementand the tilting adjustment in an automatically fashion until the tiltingmeasurement satisfies the predetermined tilting condition. Detaileddescriptions of examples of performing the tilting adjustment may referto the above descriptions in connection with FIGS. 2 and 3.

Method 600 may include performing a measurement relating to apolarization effect of a quarter-wave plate included in at least one ofthe first lens or the second lens (step 625). For example, if the firstlens 203 includes a quarter-wave plate, a measurement may be performedfor the first lens 203 relating to the polarization effect of thequarter-wave plate. Detailed descriptions of examples of performing themeasurement relating to the polarization effect of the quarter-waveplate may refer to the above descriptions in connection with FIGS. 2 and3.

Method 600 may include performing a quarter-wave plate angle adjustmentwhen the measurement does not satisfy a predetermined condition relatingto the polarization effect of the quarter-wave plate (step 630). Insteps 625 and 630, the polarization effect of the quarter-wave plate maybe verified. If the polarization effect of the quarter-wave plate is notin a desired condition, the quarter-wave plate angle may be adjusteduntil the desired polarization effect of the quarter-wave plate isachieved (e.g., the first lens 203 including the quarter-wave plate mayoutput a circularly polarized laser beam, as discussed above). Detaileddescriptions of examples of performing the quarter-wave plate angleadjustment may refer to the above descriptions in connection with FIGS.2 and 3.

Method 600 may include performing a measurement relating to apolarization effect of a reflective polarizer included in at least oneof the first lens or the second lens (step 635). For example, if thesecond lens 207 includes a reflective polarizer, a measurement relatingto the polarization effect of the reflective polarizer may be performedfor the second lens 207. Detailed descriptions of examples of performingthe measurement relating to the polarization effect of the reflectivepolarizer may refer to the above descriptions in connection with FIGS. 2and 3.

Method 600 may include performing a reflective polarizer angleadjustment when the measurement does not satisfy a predeterminedcondition relating to the polarization effect of the reflectivepolarizer (step 640). Steps 635 and 640 may be performed on the secondlens 207 to verify whether the reflective polarizer of the second lens207 has a polarization angle that results in a desired polarizationeffect. The polarization angle of the reflective polarizer may beadjusted until it is determined that the desired polarization effect hasbeen reached. Detailed descriptions of performing the reflectivepolarizer angle adjustment may refer to the above descriptions inconnection with FIGS. 2 and 3.

In some embodiments, the same station (e.g., Station 3 or Station 4) maybe used to process the first lens holder 900 (hence the first lens 203)and the second lens holder 700 (hence the second lens 207). In otherwords, the steps 625, 630, 635, and 640 may be performed at the samestation. For example, the first lens 203 and the second lens 207 may beprocessed in turn at the station in any order. When the first lens 203has been processed (e.g., when the quarter-wave plate angle adjustmenthas been performed), the first lens 203 may be moved out of the station.Then the second lens 207 may be transferred into the station andprocessed at the station (e.g., the reflective polarizer angleadjustment may be performed). After the second lens 207 is processed,the second lens 207 may be moved out of the station, such that anotherfirst lens 203 in the second assembly and validation line 262 may betransferred into the station and processed. The present disclosure doesnot limit the order in which the first lens 203 and the second lens 207are processed in the same station. In some embodiments, differentstations (e.g., Station 3 and Station 4) may be used to each process onetype of lens (e.g., first lens 203 or second lens 207).

FIG. 7 is a perspective front view of an example second lens holder 700configured to mount or for mounting a second lens. For example, thesecond lens holder 700 may be an embodiment of the second lens holder227 shown in FIG. 2, and the second lens to be held in the second lensholder 700 may be the second lens 207 shown in FIGS. 2 and 3.

As shown in FIG. 7, the second lens holder 700 may include a substantialcup-shape. The cup-shape may include a larger upper portion 705 (orfirst portion 705) and a smaller lower portion 710 (or second portion710). The upper portion 705 and the lower portion 710 each may have aroughly round shape. The upper portion 705 and the lower portion 710 areroughly round because a side of the upper portion 705 and acorresponding side the lower portion 710 may be straight, as shown inFIG. 7. The present disclosure does not limit the shape of the upperportion 705 and the lower portion 710. The upper portion 705 and thelower portion 710 may be other shapes, such as square, rectangle,triangle, etc.

As shown in FIG. 7, the upper portion 705 may define a pocket forreceiving a first lens holder. In some embodiments, the upper portion705 may include a stepped-structure including a supporting surface or ashoulder portion 715 and a wall portion 720. The supporting surface 715and the wall portion 720 each have a substantially circular shape. Thewall portion 720 may be disposed on the supporting surface 715 at anouter edge of the supporting surface 715. The wall portion 720 may besubstantially perpendicular to the supporting surface 715. In otherwords, the wall portion 720 may protrude vertically from the supportingsurface 715.

The upper portion 705 may have a first opening 725 and the lower portion710 may have a second opening 725. The lower portion 710 may include aside wall extending from the supporting surface 715 of the upper portion705 to the second opening 725. The lower portion 710 gradually reducesits dimension as it extends from the supporting surface 715 to thesecond opening 725. As shown in FIG. 7, a dimension of the upper portion705 is larger than a dimension of the lower portion 710. For example, awidth or a circumference of the first opening 725 associated with theupper portion 705 is larger than a width or a circumference of thesecond opening 730 associated with the lower portion 710.

The wall portion 720 may include a plurality of ear portions protrudingfrom the wall portion 720. For example, the wall portion 720 may includea first ear portion 731, a second ear portion 732, and a third earportion 733 each protruding from an outer surface of the wall portion720. The present disclosure does not limit the number of ear portionsthat may be included in the wall portion 720, which may be one, two,four, five, etc. Each ear portion may include a plurality of verticalholes, which may be through holes penetrating a top surface and a bottomsurface of each ear portion. For example, as shown in FIG. 7, each earportion may include a first vertical hole 741 and a second vertical hole742.

Each of the first vertical holes 741 may be configured to receive ascrew. For example, when the second lens holder 700 is mounted to arotation stage in the second assembly and validation line 262 discussedabove in connection with FIGS. 2 and 3, the screws inserted into thefirst vertical holes 741 may be used for securing the second lens holder700 to a mounting bracket of the rotation stage. The screws insertedinto the first vertical holes 741 may also be used to adjust thecentering of the second lens 207 after the second lens is mounted to thesecond lens holder 700. When the screws inserted into the first verticalholes 741 are loosened, the second lens holder 700 may be movedhorizontally to adjust the centering of the second lens holder 700relative to the rotation stage.

Each of the second vertical holes 742 may be configured to receive ascrew. When the second lens holder 700 is mounted to a mounting bracketof the rotation stage, a screw may be inserted into each of the secondvertical holes 742 for adjusting the tilting of the second lens 207. Forexample, in some embodiments, when a screw in any one of the secondvertical holes 742 is screwed in, the corresponding ear portion wherethe screw is located may be pushed up (e.g., the ear portion may bepushed up away from the mounting bracket), thereby changing the tiltingof the second lens holder 700 (and hence the second lens 207) relativeto the rotation stage (e.g., relative to the mounting bracket). In someembodiments, each of the second vertical holes 742 may receive a screwfor securing a base cover configured to mount a display to the secondlens holder 700, as discussed below in connection with FIG. 28. Thepresent disclosure does not limit the number of through holes providedon each ear portion, which may be one, three, four, etc.

The wall portion 720 may also include a plurality of side holesextending horizontally and penetrating an inner side surface and anouter side surface of the vertical wall portion 720. For example, asshown in FIG. 7, the wall portion 720 may include a first side hole 751,a second side hole 752, a third side hole 753, and a fourth side hole754. Any other suitable number of side holes may be included, such asone, two, three, five, six, etc. Each side hole may be configured toreceive a screw. In some embodiments, the screws may be configured tosecure the first lens holder 217 to the second lens holder 700 after thefirst lens holder is mounted to the second lens holder 700.

As shown in FIG. 7, the second lens holder 700 may be configured tomount or hold the second lens 207. For example, the second lens 207 maybe disposed at the second opening 725 of the lower portion 710. Thesecond lens 207 may be secured at the second opening 725 of the lowerportion 710 through any suitable methods. For example, the second lens207 may be secured to the second lens holder 700 by screws provided onthe second lens holder 700. In the embodiment shown in FIG. 7, thesecond lens holder 700 includes two side holes (first side hole 761 andsecond side hole 762) on the lower portion 710 for receiving screws thatmay be used to secure the second lens 207 to the second lens holder 700(e.g., the lower portion 710 of the second lens holder 700). In otherembodiments, the second lens 207 may be glued to the lower portion 710using a glue after the second lens 207 is inserted at the second opening730 of the second lens holder 700. For example, an ultraviolet curableglue (a UV glue) may be applied to the circumference of the second lens207 to glue the second lens 207 to the lower portion 710 of the secondlens holder 700 at or near the second opening 730.

Although not shown in FIG. 7, as described below, the first lens holder217 (with the first lens 203) may be mounted to the second lens holder700. For example, the first lens holder 217 may be disposed in thepocket defined by the upper portion 705. In some embodiments, the firstlens holder 217 may be placed on and supported by the supporting surface715 of the upper portion. The first lens holder 217 may be secured tothe second lens holder 700 using any suitable method. In someembodiments, the first lens holder 217 may be secured to the second lensholder 700 using screws, such as screws inserted into the side holes751, 752, 753, and 754 provided on the wall portion 720. In someembodiments, the first lens holder 217 may be secured to the second lensholder 700 using a glue, such as a UV curable glue.

FIG. 8 is a perspective back view of the second lens holder 700. FIG. 8shows the overall cup shape of the second lens holder 700. As shown inFIG. 7 and FIG. 8, the upper portion 705 and the lower portion 710 eachhave a cross section having a substantial D-shape, which is a circularshape with a straight side. FIG. 8 also shows that a size of the lowerportion 710 gradually reduces as it extends from the upper portion 705to the second opening 730 where the second lens 207 is mounted. As shownin FIG. 8, the wall portion 720 of the second lens holder 700 mayinclude a lower surface 810. The lower surface 810 may rest on amounting bracket when the second lens holder 700 is mounted to themounting bracket, as discussed below in connection with FIG. 12.

FIG. 9A is an exploded side view of a first lens holder 900. FIG. 9B isan exploded perspective view of the first lens holder 900. The firstlens holder 900 may be configured to mount a first lens, such as thefirst lens 203. The first lens holder 900 may be an embodiment of thefirst lens holder 217 shown in FIGS. 2 and 3. For example, the firstlens holder 900 may include three members stacked and connectedtogether, a first member 911, a second member 912, and a third member913, with the second member 912 being disposed between the first member911 and the third member 913. Each of the first member 911, the secondmember 912, and the third member 913 may include a ring-shapedstructure. Specifically, in some embodiments, the first member 911 andthe second member 912 may each have a D-shape, as shown in FIG. 9A andFIG. 9B, which matches the shape of the upper portion 705 of the secondlens holder 700. The third member 913 may have a circular shape (orregular round or ring shape). For illustrative purposes, the firstmember 911, the second member 912, and the third member 913 are shown asseparated from each other in order to show internal elements. The firstmember 911 may be configured to hold or mount the first lens 203. Forexample, the first lens 203 may be securely mounted to the first member911 by one or more screws 915 inserted in one or more side through holes916 provided on a circumferential side wall 910 of the first member 911,as also shown in FIG. 9A. The side view shown in FIG. 9A shows only oneside through hole 916. Any suitable number of side through holes 916 maybe provided on the circumferential side wall 910 of the first member911. The number of side through holes 916 may be two, three, four, etc.For example, in one embodiment, the first lens 203 may be secured to thefirst member 911 through three screws 915 (hence the first member 911may include three side through holes 916), as shown in FIG. 10. In someembodiments, the centering of the first lens 203 may be adjusted throughadjusting one or more of the screws 915.

The first member 911 and the second member 912 may be connected orcoupled together through one or more screws. Any suitable number ofscrews, such as one, two, three, four, five, six, etc., may be providedfor securing the first member 911 and the second member 912. In oneembodiment, three screws are provided from the top side of the secondmember 912. FIG. 9A and FIG. 9B only show two screws 921 and 922. Thescrews 921 and 922 may be inserted into through holes 925 and 926 (shownin FIG. 9B) provided in the second member 912 and further into holes 981and 982 (shown in FIG. 9B) provided on the first member 911 to securethe connection between the first member 911 and the second member 912.There may be a third screw (not shown in FIG. 9B) provided on the secondmember 912 near the end where the screw 941 is located. The third screwmay penetrate a though hole provided on the second member 912, and maybe received in a hole 983 (shown in FIG. 10) provided on the firstmember 911.

The third member 913 and the second member 912 may be connected usingone or more screws. The third member 913 may include a plurality ofthrough holes for receiving the one or more screws. FIG. 9B shows thathe third member 913 includes three through holes 945, 946, and 947. Anyother suitable number of through holes may be included in the thirdmember 913, such as one, two, four, five, six, etc. FIG. 9A and FIG. 9Bshow three screws 941, 942, and 943 inserted, from above the thirdmember 913, into the corresponding through holes 945, 946, and 947 tocouple the third member 913 and the second member 912. The presentdisclosure does not limit the number of screws for coupling the thirdmember 913 and the second member 912, which may be one, two, four, five,six, etc. The second member 912 may include holes (which may or may notbe through holes) configured to receive the corresponding screws 941,942, and 943, for securing the third member 913 with the second member912. In the view of FIG. 9B, only two holes 961 and 962 are shown in thesecond member 912. The second member 912 may include a third hole (notshown) for receiving screw 941.

One or more springs may be disposed between the third member 913 and thefirst member 911. For example, the one or more springs may be disposedbetween a lower portion of the third member 913 and a top portion of thefirst member 911. The each of the springs may penetrate a though hole(e.g., 992, 993) provided on the second member 912. FIG. 9A shows twosprings 931 and 932, and FIG. 9B shows two springs 932 and 933. Thus, inthe embodiment shown in FIG. 9A and FIG. 9B, there are three springs931, 932, and 933. The present disclosure does not limit the number ofsprings, which may be one, two, four, five, six, etc. The first member911 may include a depression or hole (which is not a through hole) 971,972, or 973 (shown in FIG. 10) for receiving an end of a spring.Correspondingly, the third member 913 may include a depression or hole(which is not a through hole and is not shown in FIG. 9B) for receivinganother end of the spring. When the first member 911, the second member912, and the third member 913 are assembled, the first member 911 andthe second member 912 are coupled together by screws 921 and 922 (andmaybe a third screw not visible in FIG. 9B but located on the screw 941end of the second member 912). The third member 913 may be coupled withthe second member 912 through the screws 941, 942, and 943. The springs931, 932, and 933 may be in a compressed state (e.g., loaded), applyinga resilient force on both the lower portion of the third member 913 andthe top portion of the first member 911, which pushes the third member913 apart from the first member 911 and the second member 912. When oneor more of the screws 941, 942, and 943 are adjusted, one or more of thesprings 931, 932, and 932 may push the first member 911 and the thirdmember 913 apart with a larger or smaller resilient force, therebycausing a change in a tilting angle (or tilting) of the first member 911(together with the second member 912) relative to the third member 913,which may be mounted to a rotation stage during the tilting adjustmentand may be fixed relative to the rotation stage. As a result, thetilting of the first lens 203 may be adjusted by adjusting the screws941, 942, and 943. Thus, the screws 941, 942, and 943, and the springs931, 932, and 933 may form a tilting adjustment mechanism of the firstlend holder 900.

The third member 913 may include one or more depressions or holes on aside circumferential wall 950, each depression or hole configured toreceive a screw. One or more depressions or holes may be included on theside circumferential wall 950 of the third member 913. For example, FIG.9A and FIG. 9B show two depressions or holes 951 and 952. Any othersuitable number of depressions or holes may be included, such as one,three, four, five, six, etc. When the first lens holder 900 is mountedto a rotation stage, the third member 913 may be coupled to a mountingbracket of the rotation stage. For example, the third member 913 may besecured to the mounting bracket through screws inserted into throughholes provided on the mounting bracket of the rotation stage. The screwsmay be received in the depressions or holes 951 and 952 provided on theside circumferential wall 950 of the third member 913, thereby securelycoupling the third member 913 (and hence the entire first lens holder900) with the mounting bracket of the rotation stage, which will bedescribed below. Each of the screws for securing the third member 913 tothe mounting bracket may be a push-pull type, which means turning thescrew in or out may push or pull the third member 913, thereby adjustingthe centering of the third member 913 (and hence the entire first lensholder 900 including the first lens 203 held by the first member 911)relative to the rotation stage.

FIG. 10 is a schematic illustration of a cross-sectional top view of thefirst member 911 with the first lens 203 mounted thereon. FIG. 10 showsthe ring-shaped structure of the first member 911. The second member 912may have the same ring-shaped structure. The ring-shaped structure mayappear to have a D-shape. In some embodiments, the third member 913 mayhave a matching D-shape, or may have a substantially circular ringshape, as shown in FIG. 9B, rather than having a D-shape.

As shown in FIG. 10, a plurality of side through holes 916 may beprovided on the circumferential side wall 910 of the first member 911.In the embodiment shown in FIG. 10, three side through holes 916 areincluded on the circumferential side wall 910. Any other suitable numberof side through holes may be included, such as one, two, four, five,six, etc. A plurality of screws 915 (e.g., set screws) may be insertedinto the side through holes 916 to abut against the first lens 203,thereby mounting and securing the first lens 203 to the first member911. In some embodiments, the centering of the first lens 203 may beadjusted by adjusting one or more of the screws 915. FIG. 10 also showsthree holes 981, 982, and 983 for receiving the springs 931, 932, and933. Any other suitable number of holes may be included for receivingthe springs (the number of holes may be the same as the number of thesprings). FIG. 10 further shows three holes 971, 972, and 973 forreceiving screws 921, 922, and a third screw not shown in FIG. 9B forcoupling the second member 912 with the first member 911.

FIG. 11 is a perspective view of a portion of a rotation stage with thesecond lens holder 700 mounted thereon. The second lens holder 700 maybe mounted to a rotation stage 1200 during an assembling and alignmentvalidation process discussed above in connection with the secondassembly and validation line 262 shown in FIGS. 2-3. For example, thesecond lens holder 700 may be mounted to a mounting bracket 1210 of therotation stage 1200. In some embodiments, the mounting bracket 1210 mayhave a shape that matches the shape of the second lens holder 700. Forexample, the mounting bracket 1210 may be a vertical, substantiallycircular wall. The second lens holder 700 may be supported by a topsurface of the mounting bracket 1210. For example, the lower surface 810(shown in FIG. 8) of the wall portion 720 and lower surfaces of theprotruding ear portions 731, 732, and 733 of the wall portion 720 may besupported by the top surface of the mounting bracket 1210.

The mounting bracket 1210 may include vertical holes at locationscorresponding to the first vertical holes 741 provided on the earportions 731, 732, and 733 of the second lens holder 700. The verticalholes of the mounting bracket 1210 may be connected to the firstvertical holes 741 on the second lens holder 700. A screw may beinserted into each first vertical hole 741 on the second lens holder 700and further into a corresponding vertical hole on the mounting bracket1210 such that the second lens holder 700 may be secured to the mountingbracket 1210. FIG. 11 shows three screws 1111, 1112, and 1113 insertedinto three first vertical holes 741 provided on the ear portions 731,732, and 733. The number of ear portions may be any other numbers, suchas two, four, five, six, etc. The number of first vertical holes 741 maybe any other numbers, such as two, four, five, six, etc.Correspondingly, the number of screws inserted into the first verticalholes 741 may be any other numbers, such as two, four, five, six, etc. Ascrew may be inserted into a second vertical hole 742 on the second lensholder 700. FIG. 11 shows three screws 1121, 1122, and 1123 insertedinto three second vertical holes 742 provided on the three ear portions731, 732, and 733. Each of the screws inserted into the second verticalholes 742 may abut against the top surface of the mounting bracket 1210.When the screw inserted into the second vertical hole 742 is adjusted,the tilting of the second lens holder 700 relative to the rotation stage1200 may be adjusted. For example, when the screw inserted into thesecond vertical hole 742 is further screwed in, the screw may furtherpush against the top surface of the mounting bracket 1210, and furtherpush up the second lens holder 700, thereby adjusting the tilting of thesecond lens holder 700 (and hence the second lens 207 held by the secondlens holder 700) relative to the rotation stage 1200.

FIG. 12 is a top view of the second lens holder 700 mounted on therotation stage 1200. As shown in FIG. 12, the rotation stage 1200 mayinclude an angle scale 1220 for indicating the turning angle of thesecond lens holder 700 (hence the second lens 207), which may berecorded and referred to in Station 4 as a reflective polarizer angle,as discussed above. The angle may be used for aligning the first lensholder 900 (hence the first lens 203) and the second lens holder 700(hence the second lens 207). FIG. 12 shows a screw 1311 (1312, or 1313)inserted into the first vertical hole 741 provided on the ear portion ofthe second lens holder 700. The screws 1311, 1312, 1313 may secure thesecond lens holder 700 to the mounting bracket 1210. The screws 1311,1312, 1313 may also be adjusted (e.g., loosened) to allow the centeringof the second lens holder 700 (and hence the second lens 207 mounted onthe second lens holder 700) to be adjusted relative to the rotationstage.

Although it is not clearly shown in FIG. 12, a screw may be insertedinto the second vertical hole 742 at each ear portion. The screws in thesecond vertical holes 742 may abut against the top surface of themounting bracket 1210. When any of the screws in the second verticalholes 742 is adjusted, the corresponding ear portion may be pushed up(i.e., raised up), thereby adjusting the tilting of the second lensholder 700 (and hence the second lens 207 mounted on the second lensholder 700) relative to the rotation stage 1200.

FIG. 13 is a side view of the first lens holder 900 mounted to arotation stage 1300. As shown in FIG. 13, the rotation stage 1300 mayinclude a mounting bracket 1310 configured for mounting or to mount thefirst lens holder 900. The first lens holder 900 may include the firstmember 911 that holds the first lens 203, the second member 912, and thethird member 913. The third member 913 is not visible in the view shownin FIG. 13, as it is blocked by the mounting bracket 1310. The firstmember includes the one or more side holes 916 configured to secure thefirst lens 203.

The mounting bracket 1310 may include one or more side holes on avertical wall at locations corresponding to the one or more depressionsor holes 951 and 952 provided on the third member 913 of the first lensholder 900, as shown in FIG. 9. Although the side view of FIG. 13 showsone side hole 1320 with a screw 1325 inserted therein, the mountingbracket 1310 may include any suitable number of side holes 1320, such astwo, three, four, etc. The side holes 1320 may be through holes and maybe connected with the depressions or holes 951 and 952. The screws 1325may extend throughout the side holes 1320, and further extend into thedepressions or holes 951 and 952, thereby securing the first lens holder900 on the mounting bracket 1310. In one embodiment, four side holes1320 are included in the mounting bracket 1310, and four screws 1325 maybe used to secure the first lens holder 900 on the mounting bracket1310.

In some embodiments, each of the screws 1325 may be a push-pull type.That is, adjusting the screw 1325 may push or pull the first lens holder900 in a horizontal direction (e.g., in a plane in which the first lens203 is positioned), thereby adjusting the centering of the first lensholder 900 (and hence the first lens 203 held by the first lens holder900) relative to the rotation stage 1300. Centering adjustment throughthe screws 1325 may move the optical axis of the first lens 203 tooverlap with the rotation axis of the rotation stage 1300.

One or more screws 1330 may be configured for securing a displaymounting bracket for mounting a display to the back of the first lensholder 900 during an alignment validation process, as shown in FIGS.22-23. The one or more screws 1330 may also be adjusted to change thecentering of the display relative to the first lens 203. Any suitablenumber of screws 1330 may be used, such as one, two, three, four, etc.In some embodiments, four screws 1330 are used to secure and adjust thecentering of the display.

FIG. 14 shows a top view of the first lens holder 900 mounted to therotation stage 1300. As shown in FIG. 14, the mounting bracket 1310 mayinclude a plurality of flanges 1411, 1412, 1413, 1414 (four shown inFIG. 14) extending into the inner space defined by the mounting bracket1310. The flanges may be configured to support the first lens holder 900when the first lens holder 900 is placed into the inner space defined bythe mounting bracket 1310. Any other suitable number of flanges may beincluded in the mounting bracket 1310, such as two, three, five, six,etc.

FIG. 14 further shows that the rotation stage 1300 may include an anglescale 1350 for indicating the turning angle of the first lens 203 (i.e.,the first lens holder 900), which may be recorded in Station 3 as aquarter-wave plate angle. The angle may be used for aligning the firstlens holder 900 (hence the first lens 203) and the second lens holder700 (hence the second lens 207).

FIG. 15 illustrates the second lens holder 700 and the first lens holder900 mounted to the rotation stage 1300. The purpose of FIG. 15 is toshow that after the first lens holder 900 is mounted to the rotationstage 1300 and the second lens holder 700 is mounted to the rotationstage 1200 (not shown in FIG. 15 for the purpose of clarity), they aremoved approaching each other in order to couple with one another, asshown in FIG. 16.

FIG. 16 illustrates that that the rotation stages 1200 and 1300 arealigned and/or coupled together. At this state, an alignment validationmay be performed to verify the polarization alignment between the firstlens 203 and the second lens 207, as discussed above in connection withStation 5 shown in FIG. 3. After the first lens 203 and the second lens207 are aligned, the first lens holder 900 may be separated from therotation stage 1300 and may be coupled with the second lens holder 700.To transfer the first lens holder 900 from the rotation stage 1300 tothe second lens holder 700, screws 1610 provided at side holes 751, 752,753, and 754 of the second lens holder 700 may be fastened to secure thecoupling between the first member 911 of the first lens holder 900 andthe second lens holder 700, and screws 1320 on the mounting bracket 1310may be loosened to release the coupling between the first lens holder900 and the mounting bracket 1310 of the rotation stage 1300.

FIG. 17 illustrates the first lens holder 900 coupled to the second lensholder 700 after the rotation stage 1300 is separated from the firstlens holder 900. As shown in FIG. 17, after the rotation stage 1300 isremoved, the second member 912 and the third member 913 of the firstlens holder 900 are exposed. For illustrative purposes, a portion of thesecond lens holder 700 is removed to show the first member 911 of thefirst lens holder 900.

FIG. 18 illustrates a perspective view of an assembly of the first lensholder 900 and the second lens holder 700, if the rotation stages 1200and 1300 are both removed. The first member 911 of the first lens holder900 may be secured to the wall portion 720 of the second lens holder 700through screws 1610 (shown in FIG. 16) inserted into side holes 751,752, 753, and 754 (only side hole 753 is visible in FIG. 18). In someembodiments, the screws 1610 may be adjusted to adjust the alignment(e.g., the centering) of the first member 911 of the first lens holder900 (hence the first lens 203) relative to the second lens holder (hencerelative to the second lens). That is, in some embodiments, the opticalaxis of the first lens 203 may be adjusted to align with the opticalaxis of the second lens 207 by adjusting the screws 1610 provided on thesecond lens holder that also functions to secure the first member 911 ofthe first lens holder 900 to the second lens holder 700. The assemblyshown in FIG. 18 may be referred to as a housing assembly 1800 formounting lenses, such as the first lens 203 and the second lens 207. Thehousing assembly 1800 includes the first lens holder 900 and the secondlens holder 700. The second lens holder 700 includes the upper portion705 and the lower portion 710. As described above in connection withFIG. 7, the upper portion 705 defines a pocket to receive and mount thefirst lens holder 900. The lower portion 710 is configured to mount thesecond lens 207.

FIG. 19 illustrates a perspective view of the second lens holder 700mounted to the rotation stage 1200, with the first lens holder 900coupled to the second lens holder 700. The second member 912 and thethird member 913 have been removed from the first lens holder 900. Thesecond member 912 and the third member 913 may be removed after analignment validation using a display has been performed, which isdiscussed above in connection with Station 5 shown in FIG. 3, and whichwill also be described below. In the view of FIG. 19, only the firstmember 911 and the first lens 203 remain in the first lens holder 900.As shown in FIG. 19, the first member 911 (and hence the first lens 203)of the first lens holder 900 may be secured to second lens holder 700through screws 1610 inserted into side holes 751, 752, 753, and 754provided on the side wall 720 of the second lens holder 700. Only onescrew 1610 is shown in FIG. 19 for illustrative purposes. In someembodiments, the second member 912 and the third member 913 may beremoved after the first member 911 is secured to the second lens holder700 using a suitable method, e.g., using gluing.

FIG. 20 is a perspective view of an optical assembly 2000 including thefirst lens holder 900, the first lens 203 mounted to the first lensholder 900, the second lens holder 700, and the second lens 207 (notvisible in FIG. 20) mounted to the second lens holder 700. The firstlens holder 900 and the second lens holder 700 are coupled together. Therotation stages 1200 and 1300 have been removed. In addition, in thehousing assembly 1800 (shown in FIG. 18), the second member 912 and thethird member 913 of the first lens holder 900 have been removed. Thefirst lens 203 and the second lens 207 are aligned to produce a desiredpolarization effect. The first lens 203 and the second lens 207 may forma polarization sensitive lens. In some embodiments, a first surface(opposite to the surface visible in FIG. 20) of the first lens 203facing the second lens 207 may be in parallel with a second surface ofthe second lens 207 facing the first surface of the first lens 203. Eachof the first surface of the first lens 203 and the second surface of thesecond lens 207 may be a flat surface or may be a curved surface. Insome embodiments, the first lens 203 and the second lens 207 may beembodiments of the first optical element 101 and the second opticalelement 102 shown in FIG. 1, respectively. The optical assembly 2000including the first lens 203 and the second lens 207 may be apolarization sensitive optical assembly.

As shown in FIG. 20 and FIG. 7, the first lens holder 900 may fit withthe first opening 725 of the second lens holder 700, and may besupported by the supporting surface 715 (shown in FIG. 7). The firstmember 911 may rest on the supporting surface 715. The first lens 203and the second lens 207 may be aligned together such that they produce adesired polarization effect. The optical assembly 2000 may represent aproduct produced by the full automation assembly line, such as thesecond assembly and validation line 262 (e.g., at Station 5), in whichthe centering adjustment and the tilting adjustment of the first lens203 and the second lens 207 have been completed (in Station 1 andStation 2). In addition, the quarter-wave plate angle adjustment of thefirst lens 203 and the reflective polarizer angle adjustment have beencompleted (in Station 3 and Station 4). In some embodiments, to furthersecuring the connection between the first lens holder 900 (e.g., thefirst member 911) and the second lens holder 700, a glue, such as aUV-curable glue, may be applied to the gap between the second lensholder 700 and the first lens holder 900 to permanently fix the couplingbetween the first lens holder 900 and the second lens holder 700. Insome embodiments, the application of the glue may be performed beforethe second member 912 and the third member 913 of the first lens holder900 are removed. In some embodiments, the optical assembly 2000 mayrepresent an intermediate product produced in the process performedthrough the full automation assembly line, with the final optical devicealso including a display, as discussed below. FIG. 20 also shows thelower portion 710 and the upper portion 705. Screws 761 and 762 may beconfigured to secure the second lens 207. In some embodiments, thescrews 761 and 762 may be omitted when other securing methods, such asgluing, are used to secure the second lens 207 to the second lens holder700.

FIG. 21 is a top view of the optical assembly 2000. In the view of FIG.21, the lower portion 710 of the second lens holder 700 is not visible.

Next, the system for mounting a display will be described. FIG. 22 showstwo rotation stages 1200 and 1300 facing each other. The rotation stage1200 includes the second lens holder 700 mounted thereon. The rotationstage 1300 includes the first lens holder 900 mounted thereon (notvisible in FIG. 22). In addition, a display 2200 is mounted to the backof the first lens holder 900 using a display mounting bracket 2210. Thedisplay 2200 may be an embodiment of the display 206 shown in FIG. 3.

FIG. 23 shows another perspective view of the two rotation stages. FIG.23 shows that the two rotation stages 1200 and 1300 are moved close toone another such that the first lens holder 900 (hence the first lens203) and the second lens holder 700 (hence the second lens 207) may bealigned. For a side view of the two rotation stages coupled together,one can refer to FIG. 16. As shown in FIG. 23, The display 2200 ismounted at the back side of the first lens holder 900 (hence the firstlens 203) using the display mounting bracket 2210. The display mountingbrackets 2210 may include four arms resting on a supporting surface ofthe mounting bracket 1310. Four screws, such as four screws 1330 shownin FIG. 13, may be used to secure and adjust the centering of thedisplay mounting bracket 2210 (and hence the display 2200) relative tothe centering of the first lens 203. An alignment validation may beperformed to verify the polarization alignment between the first lens203 and the second lens 207. As discussed above in connection withStation 5 shown in FIG. 3, the alignment validation may use the display2200 (which may be an embodiment of the display 206 shown in FIG. 3) andthe camera 354 (shown in FIG. 3). The alignment validation may beperformed with the display 2200 mounted to the rotation stage 1300.Depending on the alignment validation results, fine-tuning may beperformed to adjust the alignment between the first lens holder 900 andthe second lens holder 700. The alignment of the display 2200(including, e.g., distance, centering, and tilting of the display 2200)with respect to the first lens 203 and the second lens 207 may also beadjusted.

FIG. 24 shows the display 2200 attached to the optical assembly 2000(not visible in FIG. 24) through a base cover 2400. After the alignmentvalidation is performed using the configuration shown in FIG. 23, therotation stage 1300 may be removed. The display 2200 may be re-attachedto the optical assembly 2000 formed by the second lens holder 700 andthe first lens holder 900 (the first member 911 and the first lens 203only). The display 2200 may be mounted to the base cover 2400, and thebase cover 2400 may be mounted to the optical assembly 2200 throughscrews 2410. Although FIG. 24 shows three screws 2410 for mounting thebase cover 2400 to the optical assembly 2000, any other suitable numberof screws may be used. Correspondingly, the base cover 2400 may includeany suitable number of through holes for receiving the screws. Thescrews 2410 may be adjusted to change the distance between the display2200 and the optical assembly 2000 (e.g., the first lens 203), and tochange the tilting of the display 2200. The distance between the display2200 and the optical assembly 2000 also determines the virtual imagedistance of entire optical device.

FIG. 25 shows a perspective view of an optical device 2500 including theoptical assembly 2000 and the display 2200, with all of the rotationstages removed. FIG. 25 shows a perspective viewed from the side of thebase cover 2400.

FIG. 26 shows a perspective view of the optical device 2500 includingthe optical assembly 2000 and the display 2200 mounted on the base cover2400. FIG. 26 shows a perspective viewed from the side of the secondlens holder 700.

FIG. 27 is a perspective view of the base cover 2400. As shown in FIG.27, the base cover 2400 may include an opening 2700 in the center forreceiving and mounting the display 2200. The opening 2700 may include ashape that matches the shape of the display 2200.

Embodiments of the disclosure may include or be implemented inconjunction with an artificial reality system. Artificial reality is aform of reality that has been adjusted in some manner beforepresentation to a user, which may include, e.g., a virtual reality (VR),an augmented reality (AR), a mixed reality (MR), a hybrid reality, orsome combination and/or derivatives thereof. Artificial reality contentmay include completely generated content or generated content combinedwith captured (e.g., real-world) content. The artificial reality contentmay include video, audio, haptic feedback, or some combination thereof,and any of which may be presented in a single channel or in multiplechannels (such as stereo video that produces a three-dimensional effectto the viewer).

Additionally, in some embodiments, artificial reality may also beassociated with applications, products, accessories, services, or somecombination thereof, which are used to, e.g., create content in anartificial reality and/or are otherwise used in (e.g., performactivities in) an artificial reality. The artificial reality system thatprovides the artificial reality content may be implemented on variousplatforms, including a head-mounted display (HMD) connected to a hostcomputer system, a standalone HMD, a mobile device or computing system,or any other hardware platform capable of providing artificial realitycontent to one or more viewers.

The foregoing description of the embodiments of the disclosure has beenpresented for the purpose of illustration; it is not intended to beexhaustive or to limit the disclosure to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the abovedisclosure.

Various embodiments have been described to illustrate the exemplaryimplementations. It should be understood by those skilled in the artthat the present disclosure is not limited to the specific embodimentsdescribed herein and that various other obvious changes, rearrangements,and substitutions will occur to those skilled in the art withoutdeparting from the scope of the disclosure. Thus, while the presentdisclosure has been described in detail with reference to the abovedescribed embodiments, the present disclosure is not limited to theabove described embodiments, but may be embodied in other equivalentforms without departing from the scope of the present disclosure, whichis determined by the appended claims.

What is claimed is:
 1. A housing assembly for mounting a first lens anda second lens, comprising: a first lens holder comprising a ring-shapedstructure configured to mount the first lens; and a second lens holdercomprising a cup-shaped structure, the cup-shaped structure comprisingan upper portion configured to mount the first lens holder, and a lowerportion configured to mount the second lens, wherein the upper portionof the second lens holder comprises a supporting surface configured tosupport the first lens holder and a wall portion extending from thesupporting surface toward the first lens holder, and wherein the firstlens holder is mounted to the second lens holder, and the upper portionof the second lens holder comprises a plurality of side holespenetrating through the wall portion of the upper portion in a radialdirection parallel to the supporting surface of the second lens holder,the side holes configured to receive a plurality of screws for securingthe first lens holder to the second lens holder, and for adjusting analignment between the first lens holder and the second lens holder. 2.The housing assembly of claim 1, wherein the cup-shaped structurecomprises a first opening provided at the upper portion and a secondopening provided at the lower portion, the first opening having a firstdimension that is greater than a second dimension of the second opening.3. The housing assembly of claim 1, wherein the wall portion extendsperpendicularly from the supporting surface toward the first lensholder.
 4. The housing assembly of claim 1, wherein the wall portioncomprises a plurality of ear portions configured to mount on a mountingbracket of a rotation stage.
 5. The housing assembly of claim 4, whereineach of the plurality of ear portions comprises one or more verticalholes configured to receive one or more screws, at least one of the oneor more screws being adjustable to change at least one of a centering ofthe second lens or a tilting of the second lens.
 6. The housing assemblyof claim 1, wherein the first lens holder comprises a first memberconfigured to mount the first lens, and wherein the first membercomprises a plurality of side holes provided on a circumferential sideto receive a plurality of screws for securing the first lens.
 7. Thehousing assembly of claim 6, wherein the first lens holder furthercomprises: a second member; a third member, wherein the first member,the second member, and the third member are stacked together with thesecond member disposed between the first member and the third member. 8.The housing assembly of claim 7, wherein the first lens holder furthercomprises: one or more springs disposed between a lower portion of thethird member and a surface top portion of the first member, the one ormore springs being in a compressed state when the first member and thethird member are connected.
 9. The housing assembly of claim 8, whereinthe first lens holder further comprises: one or more screws configuredto connect the first member with the third member, wherein the one ormore screws are configured to be adjustable to cause a tilting of thefirst lens to be changed by a resilient force exerted by the one or moresprings.
 10. The housing assembly of claim 8, wherein the first lensholder further comprises: one or more screws configured to connect thethird member with the second member.
 11. The housing assembly of claim7, wherein the third member further comprises one or more side holesprovided on a side wall of the third member and configured to receiveone or more screws that secure the third member to a mounting bracket ofa rotation stage.
 12. An optical assembly, comprising: a first lensholder; a first lens mounted to the first lens holder; a second lensholder; and a second lens mounted to the second lens holder, wherein thefirst lens holder is mounted to the second lens holder, and the firstlens is aligned with the second lens, and wherein the second lens holdercomprises a cup-shaped structure having an upper portion configured tomount the first lens holder, and a lower portion configured to mount thesecond lens, wherein the upper portion of the second lens holdercomprises a supporting surface configured to support the first lensholder and a wall portion extending from the supporting surface towardthe first lens holder, and wherein the upper portion of the second lensholder comprises a plurality of side holes penetrating through the wallportion of the upper portion in a radial direction parallel to thesupporting surface of the second lens holder, the side holes configuredto receive a plurality of screws for securing the first lens holder tothe second lens holder, and for adjusting an alignment between the firstlens holder and the second lens holder.
 13. The optical assembly ofclaim 12, wherein the first lens holder comprises a ring-shapedstructure.
 14. The optical assembly of claim 12, wherein the cup-shapedstructure comprises a first opening provided at the upper portion and asecond opening provided at the lower portion, the first opening islarger than the second opening.
 15. An optical device, comprising: anoptical assembly, comprising: a first lens holder; a first lens mountedto the first lens holder; a second lens holder; and a second lensmounted to the second lens holder, wherein the first lens holder ismounted to the second lens holder, and the first lens is aligned withthe second lens, wherein the second lens holder comprises a cup-shapedstructure having an upper portion configured to mount the first lensholder, and a lower portion configured to mount the second lens, whereinthe upper portion of the second lens holder comprises a supportingsurface configured to support the first lens holder and a wall portionextending from the supporting surface toward the first lens holder, andwherein the upper portion of the second lens holder comprises aplurality of side holes penetrating through the wall portion of theupper portion in a radial direction parallel to the supporting surfaceof the second lens holder, the side holes configured to receive aplurality of screws for securing the first lens holder to the secondlens holder, and for adjusting an alignment between the first lensholder and the second lens holder; a display; and a base coverconfigured to mount the display, the base cover being mounted to thesecond lens holder of the optical assembly.
 16. The optical assembly ofclaim 12, wherein the first lens is aligned with the second lens with asurface of the first lens being in parallel with a surface of the secondlens.
 17. The optical device of claim 15, wherein the first lens isaligned with the second lens with a surface of the first lens being inparallel with a surface of the second lens.